纳米隔热材料热辐射特性的理论计算

Theoretical Computation on Thermal Radiative Properties of Nanoinsulation Materials

高温下纳米隔热材料内热辐射的影响将显著增强,其热辐射特性对热辐射传热有很大影响。为了认识高温纳米隔热材料的热辐射特性,采用Mie理论建立了掺杂纤维增韧剂和遮光剂的纳米隔热材料热辐射特性理论计算方法,编写了纳米隔热材料热辐射特性计算程序,对某纳米隔热材料的热辐射特性进行了理论研究,得到了光谱衰减系数、光谱散射反照率以及全光谱平均辐射特性参数及散射相函数。理论模拟结果表明:在3～9.5μm波长范围内,纳米隔热材料对热辐射具有强烈的衰减作用,对3～7μm的热辐射呈现强烈的散射特征,对7～9.5μm的热辐射,随波长增大散射特征逐渐减弱,对9.5μm的热辐射呈现较强的吸收特征。在300～1 300 K,该纳米隔热材料全光谱平均衰减系数>5×104 m-1,平均散射反照率>0.96,具有较强的前向散射特征,这些特征来源于遮光剂粒子,增韧剂影响很小。

Thermal radiative properties have significant influences on the radiative heat transfer process which be-comes obvious in nanoinsulation materials at high temperature.In order to better understand the materials radiative properties,a theoretical method based on Mie theories is presented for nanoinsulation materials containing both rein-forcement fibers and opacifiers.Corresponding computer codes are developed and the thermal radiative properties are studied theoretically for a specific nanoinsulation material.The parameters describing the radiative properties are ob-tained which include the spectral extinction coefficient and scattering albedo,the Rosseland averaged extinction coeffi-cient and scattering albedo,the Rosseland averaged scattering phase function etc.Results from theoretical simulation in-dicate that for the wavelength studied between 3 μm and 9.5 μmt,he material has strength extinction to thermal radia-tion.The material exhibits highly scattering for thermal radiation with the wavelength between 3 μm and 7 μm.For thermal radiation with the wavelength between 7 μm and 9.5 μm,the scattering phenomenon becomes weak with the in-crease of wavelength.For thermal radiation with the wavelength of 9.5 μm,the material exhibits obviously absorbing.Under the temperature between 300 K and 1 300 Kt,he rosseland averaged extinction coefficient of the nanoinsulation material is greater than 50 000 m-1a,nd its averaged scattering albedo is greater than 0.96.The highly forward scattering characteristic of the material results from the opacifier and the reinforcement fibers in the material have less influences.